Orthogonal frequency division multiplexing (OFDM) is a popular multicarrier modulation method that has been adopted in numerous wireless networking and broadcasting standards such as IEEE 802.11a/g/p, LTE, and DVB-T/T2. Some of the key advantages of OFDM are its high spectral efficiency, robustness to inter-symbol interference (ISI) caused by multipath, and its ability to equalize wideband channels. However, OFDM is sensitive to time and frequency offsets, which need to be estimated in order to correctly demodulate the received data.
Recent work has focused on blindly estimating these offsets. Non-data-aided estimators have the advantage of not requiring any known training data, thus preserving high bandwidth efficiency. A major drawback to many time offset estimators is that they are designed for single path channels and their estimation performance degrades in multipath channels. Even estimators that are designed for multipath channels tend to have high computational complexities.
A need exists for a new joint symbol time offset (STO) and carrier frequency offset (CFO) estimator for OFDM systems when the channel order is less than or equal to the length of the cyclic prefix that is low-complexity and does not suffer performance degradation in multipath channels.